1. Field of the Invention
The present invention relates to a printing apparatus and, more particularly, to a printing apparatus for printing on a cut sheet supplied from a feed cassette.
2. Discussion of the Related Art
In a conventional printing apparatus, various types of sensors are provided in the course of a path traveled by a supply of sheets from a feed cassette, and the most suitable print condition is determined based on signals indicative of sheet information (for example, information about the size of a sheet, the thickness of a sheet, etc.) detected by the sensors, thereby enabling print adjustments to be made on the sheet in accordance with the detected signals.
Such sensors have been used, for example, to detect the thickness of the sheet for thereby appropriately setting an interval, or head gap, between a print head and the sheet, and, more specifically, for setting an interval between a print wire of the print head and the sheet or an interval between a tip portion of an ink jet nozzle of the print head and the sheet. Such sensors have also been used to detect the width of the sheet for thereby adjusting a print allowance range, a print start position, etc.
The above-described conventional printing apparatus does not, however, perform in a satisfactory manner for reasons set forth herein.
When one kind of sheet differs from another kind of sheet in elastic coefficient of the sheet or friction coefficient on the surface of the sheet, even when the sheets have equal thickness, the suitable nip pressure for the one kind of sheet provided by feed rollers of the apparatus is different from the suitable nip pressure for the other kind of sheet. Therefore, if the suitable nip pressure is not set in accordance with the elastic coefficient of the sheet or the friction coefficient of the surface of the sheet, a mis-feed can occur such as a superimposed sheet delivery, omission, and an excessive skew causing the sheets to be obliquely delivered in excess.
Various types of sensors can be added or provided in order to avoid such inconvenience. However, limitations are imposed on the number of sensors which can be provided in the course of a restricted sheet supply path. When it is necessary to detect the elastic coefficient of the sheet, the friction coefficient thereof or the like, the arrangement of the respective sensors becomes cumbersome, thus leading to an unreal solution. Various sheet information for each sheet can be input by a keyboard or the like. Errors can, however, occur in the input of information by the operator. Unnecessary labor is further required to input the information.